The present invention relates generally to material handling equipment, including but not limited to mobile machinery of the type used for material handling jobs that require moving or positioning of a load. In particular, the present invention relates to a load handler with a modular frame and the manufacture and assembly of the frame and loader and components that may be used therein.
In construction jobs, it is desirable to lift heavy loads such as equipment, building materials, or earth, and to move, position or place the loads at other locations. This may require movement of a load high above and forward from the loader. Load handling vehicles, also referred to as loaders, loader vehicles or load handlers, employ pivoting booms that may be raised or lowered about a pivot point on the loader frame, and may be telescoped to move the load to the desired position. Attachments for the booms may be used for performing various jobs. For example, fork and bucket attachments may be used for moving materials like bricks or earth. Other attachments may be used for pouring concrete, handling roof trusses, boring holes in the earth, or other tasks.
The capability of loader vehicles is measured in some respects by how heavy a load it can lift and how high it can lift a load. For example, loaders may lift loads weighing up to twenty to sixty thousand pounds or more, to heights of up to twenty to one hundred feet or higher. The factors affecting the loader capability include, for example, the strength of the boom structure, the power of hydraulic cylinders for lifting and telescoping the boom, and the stability of the loader vehicle against tipping over. The stability depends on factors such as the weight of the loader vehicle, the positioning of the boom pivot point on the vehicle, the front to back and side to side spacing of the wheels, and the center of gravity of the load and vehicle.
In use, a load handling vehicle is subjected to tremendous stress forces resulting from the positioning of heavy loads at the end of the boom. These stress forces include twisting forces about the longitudinal axis of the frame of the vehicle. Depending on the work site conditions, the load handler may have to travel over or stand on uneven surfaces while carrying or positioning the load. This may increase the stress forces, such as due to leveling forces exerted by stabilizing hydraulic cylinders acting between the axles and the vehicle frame. Consequently, the vehicle frame may be subjected to compound bending and twisting stress forces due to the heavy loads and movement. The vehicle frame is desirably constructed with sufficient stiffness and torsion strength to withstand these forces without experiencing unacceptable deformation.
To achieve sufficient stiffness and torsion strength, frames for loader vehicles have been built using a box-shaped generally closed overall frame cross-section configuration. Although such a configuration provides good stiffness, the box shape may require that the boom pivot point be positioned relatively high. A relatively lower boom pivot point may be desirable to lower the center of gravity to increase stability of the vehicle. Some load handlers are configured to achieve a low boom pivot point by mounting the vehicle engine and operator cab to the sides of the vehicle with the boom nestled between them in the boom's lowered position. This configuration also provides a good field of vision for the operator in many uses of the load handler. However, to accommodate the lower boom position, the top of the box-shaped closed overall frame cross-section configuration may have to be opened up to an extent, thus adversely affecting stiffness and torsion strength. For example, such opened frames may lose stiffness and torsion strength particularly with respect to twisting forces along the vehicle front to rear longitudinal axis, with twisting occurring along the length of the frame's longitudinal structural beam members, or side rails.
In addition, the frames of load handling vehicles are commonly made in a unitary construction with components particularly designed for a particular vehicle capability. The frames are assembled using a “cell” type manufacturing process in which all the components for the frame of the vehicle are brought to a location and all the components are assembled at that location. Such an assembly process is relatively inefficient in that it requires dedicated floor space for extended periods of lead time during assembly.